Production of fibers from phenylene sulfide polymers

ABSTRACT

Strong, high modulus, high-melting, non-burning fibers are formed from aromatic sulfide polymers, such as phenylene sulfide polymers, by melt spinning an aromatic sulfide polymer having a melt flow in the range of from 75 to 800 followed by drawing the fibers in the molten state, cooling the fibers, and, optionally, drawing the cooled fibers in the solid state.

United States Patent Short et al. July 15, 1975 1 PRODUCTION OF FIBERSFROM [56] References Cited PHENYLENE SULFIDE POLYMERS UNITED STATESPATENTS [75] Inventors: James N. Short, Bartlesville, Okla; 3,354,12911/1967 Edmonds et a1. 260/79 Lee 0 Edmonds deceased late of Gobran eta1 1 11 1 3,519,606 7/1970 Conciatori 264/176 F 532 :33 g f g g3,524,835 8/1970 Edmonds Ct :11. 260/79 Edmonds both Bartlesme 3,539,67611/1970 Polcstak 264/210 F 3,562,199 2/1971 Hill et a1. 260/79 Okla.[73] Assignee: Phillips Petroleum Company, Primary Examiner-Jay l-l. Woo

Bartlesville, Okla. [57] ABSTRACT [22] Flled' Apr. 1974 Strong, highmodulus, high-melting, non-burning fi- [21] Appl. No.: 458,701 bers areformed from aromatic sulfide polymers, such Related us. Application Dataas phenylene sulfide polymers, by melt spinning an ar- C in t of S r No355 004 A til 27 omatic sulfide polymer having a melt flow in the range0 mualon' 7 p of from 75 to 800 followed by drawing the fibers in 1973,abandoned, which is a continuation-in-part of Sen No. 237,881 March 241972, abandonedthe molten state, cooling the fibers, and, optionally,

drawing the cooled fibers 1n the solid state.

[52] US. Cl 264/210 F; 264/176 F; 264/290 R [51] Int. Cl. ..D01D 5/12[58] Field of Search 264/176 F, 210 F, 290 R; 7 Claims, N0 DrawingsPRODUCTION OF FIBERS FROM PHENYLENE SULFIDE POLYMERS This is acontinuation-in-part application of our copending application havingSer. No. 355,004, filed Apr. 27, 1973 and now abandoned, which in turnis a continuation-in-part application of our application having Ser. No.237,881, filed Mar. 24, 1972, now abandoned.

This invention relates to the production of fibers from aromatic sulfidepolymers. In accordance with another aspect, this invention relates to aprocess for producing strong, high modulus, non-burning fibers fromphenylene sulfide polymers by melt spinning, drawing the melt-spunfilaments in the molten state, cooling the filaments, and, optionally,drawing the filaments in the solid state. In accordance with a furtheraspect, this invention relates to the formation of strong, high modulus,high-melting, non-burning fibers from phenylene sulfide polymers bypartially curing the polymers by heating the polymers at an elevatedtemperature and for a period of time sufficient to increase themolecular weight of the polymers (reduce melt flow) prior to meltspinning. In accordance with another aspect, phenylene sulfide polymersare oxidatively cured to increase the molecular weight (reduce meltflow) prior to melt spinning followed by drawing of the melt-spunfilaments in the molten state, cooling the filaments, and finallydrawing the filaments in the solid state to produce strong,high-modulus, high-melting, non-burning fibers which can be formed intovarious articles of manufacture.

Articles made from the fibers of the invention possess many desirableproperties because of the strength, high melting point and non-burningcharacteristics of the fibers. The articles and fibers from which theyare made are also attractive for use in corrosive atmospheres andapplications because the polymers from which the fibers are made arehighly resistant to most chemicals including commonly used acids andbases. The fibers can be formed into yarn and fabrics formed from theyarn by knitting, weaving or other known means for producing fabricsincluding non-woven fab- I'ICS.

Aromatic sulfide polymers such as phenylene sulfide polymers ranging inconsistency from viscous liquids to crystalline solids are known. Whilesuch polymers exhibit desirable properties for many applications such ascoating compositions, the unmodified polymers normally possessrelatively high melt flow, that is, above 4,000, as measured in gramsper 10 minutes by ASTM method D-l238-70 modified for operation at 650F(343C) with a 5 kg weight. This high melt flow inhibits the use of thepolymers in the production of fibers. Since most of the polymers possessthe very desirable properties of high melting points [285C forpoly(phenylene sulfide)] and are non-burning, it is desirable to modifythe polymers to permit their conversion into fibers. The presentinvention is directed to a process for the production of strong,high-modulus, high-melting, non-burning fibers from modified phenylenesulfide polymers and the resulting fiber product.

In accordance with the invention, it has been found that aromaticsulfide polymers such as phenylene sulfide polymers can be melt spuninto fibers with highly desirable properties if the polymers are atleast partially cured before melt spinning in order to reduce the meltflow of the polymers to a prescribed range.

Accordingly,*an object of this invention is to improve the processingcharacteristics of aromatic sulfide resins such as phenylene sulfidepolymers.

Another object of this invention is to provide a process for theproduction of fibers from phenylene sulfide polymers.

A further object of this invention is to provide strong, high-modulus,high-melting, non-burning fibers from phenylene sulfide polymers.

Another object of this invention is to provide fibers from phenylenesulfide polymers having desirable properties that can be formed intoarticles of manufacture such as fabrics, yarn, etc.

A further object of this invention is to provide an improved method forthe production of strong, highmodulus, high-melting, non-burning fibersfrom phenylene sulfide polymers. For purposes of this disclosure, thewords filaments and fibers are used interchangeably to indicate anindeterminate length of polymer extrudate suitable for textilemanufacture.

In accordance with the invention, strong, highmodulus, high-melting,non-burning fibers are produced from aromatic sulfide polymers such asphenylene sulfide polymers by melt spinning a polymer which has beenpartially cured to a melt flow in the range of to 800 and then drawingthe melt-spun filaments in the molten state. The melt-drawn fibers canbe additionally improved by drawing in the solid state after cooling.

The resulting fibers formed according to the invention have a very highmelting point [285C for poly(- phenylene sulfide)], are non-burning asthey have an LOI (Limiting Oxygen Index) of 35 (will not burn in anatmosphere containing less than 35 volume percent oxygen), and arehighly resistant to chemical attack. Fabrics made from these fibers areespecially suitable for hightemperature applications such as industrialfilter bags, for nonburning applications such as draperies, upholstery,wall coverings, clothing, etc., and for other applications where thespecial properties of the fibers are desired.

More specifically, in accordance with one embodiment of the invention, aprocess is provided for the production of strong, high-modulus,high-melting, nonburning fibers from phenylene sulfide polymers byheating such polymers having an inherent viscosity of 0.15 to 0.25 at anelevated temperature for a period of time sufficient to at leastpartially cure the polymer and thus produce a polymer with a melt flowin the range of 75 to 800, and then melt spinning the partially curedpolymer through spinneret orifices having diameters in the range of 5 to25 mils, followed by drawing the thus melt-spun filaments while still inthe molten state at least tenfold, that is, the linear speed at whichthe filaments are wound on take-up rolls is ten times the linearvelocity of the molten polymer through the spinneret orifices. It isalso possible, of course, to extrude larger filaments through orificesof 40 mils or greater diameter in order to make fibers for bristles,cordage, etc.

In accordance with another embodiment of the in vention, melt-spun,strong, high-modulus, highmelting, non-burning fibers of phenylenesulfide polymers are formed from at least partially cured phenylenesulfide polymers having a melt flow of 75 to 800.

In accordance with still another embodiment of the invention, themelt-spun fibers of at least partially cured phenylene sulfide polymershaving a melt flow of 75 to 800, which are preferably drawn in the solidstate subsequent to melt spinning, are formed into various articles ofmanufacture such as yarn, fabrics, and the like.

The term phenylene sulfide polymer as used in this specification isintended to include polymers of the type which are prepared as describedin US. Pat. No. 3,354,129, issued Nov. 21, 1967, to Edmonds and Hill,and which can be at least partially cured to obtain poly mers with amelt flow of 75 to 800. Melt flow of these polymers is measured by ASTMmethod D-l238-70 modified for operation at 650F with a piston load of 5kilograms. As disclosed in the Edmonds and Hill patent, these polymerscan be prepared by reacting a polyhalo-substituted aromatic compoundcontaining unsaturation between adjacent ring atoms and a mixture inwhich at least one alkali metal sulfide is contacted with at least oneorganic amide. The resulting polymer contains the aromatic structure ofthe polyhalo-substituted aromatic compound coupled in repeating unitsthrough a sulfur atom. The polymers which are preferred for use in thisinvention, because of their high thermal stability and availability ofraw materials, are those polymers having the repeating unit RS where Ris phenylene or a lower alkyl-substituted derivative thereof. By loweralkyl is meant alkyl groups having 1 to 6 carbon atoms such as methyl,propyl, isobutyl, n-hexyl, and the like. Thus, the term phenylenesulfide polymers is intended to include not only the phenylene group butalso the lower alkyl substituted phenylene groups. The preparation ofsuch polymers is well disclosed in the above-mentioned patent of Edmondset al. In a presently preferred embodiment, poly(phenylene sulfide) isprepared by reacting pdichlorobenzene with a mixture in which sodiumsulfide is contacted with N-methyl-2-pyrrolidone as described in ExampleI in the Edmonds and Hill patent. Other polymers prepared as describedin the Edmonds and Hill patent are suitable for preparation of thefibers of our invention providing the polymers can be cured to a meltflow in the 75 to 800 range.

The preferred polymers for use in our invention are those havingmelting-point temperatures above about 200C. The preferred phenylenesulfide polymers can have melting-point temperatures in the range fromabout 200C (392F) to about 330C (626F). Polymers of phenylene sulfideusually have melting points in the range from about 250C (482F) to 300C(572F). However, it is believed that other aromatic sulfide polymerssuch as phenylene sulfide polymers having higher melting temperaturesranging up to about 500C can be satisfactorily melt spun into fibersaccording to the invention. In the event that polymers having meltingtemperatures above about 325C are used, a modified melt flow evaluationprocedure would need to be developed as the ASTM method D-l2- 38-70, aspresently modified, is capable of measuring the melt flow properties ofpolymers having melting temperatures below 650F (343C).

The preferred polymers before curing have an inherent viscosity asmeasured in l-chloronaphthalene at 206C at a polymer concentration of0.4 g/100 ml solution of at least 0.15, more preferably between 0.15 and0.25, and in some instances between 0.18 and 0.22. Melt flow of thepolymers before curing is usually above 4,000, much too high forpreparation of suitable fibers. After curing, it is difficult, if notimpossible, to measure inherent viscosity of the polymer because of itsvery high molecular weight. We, therefore, use melt flow as a morereliable measure of the suitability of the polymer for the preparationof fibers.

In accordance with the invention, a virgin phenylene sulfide polymerhaving a melt flow of 800 or higher is heated at an elevated temperaturefor a period of time sufficient to at least partially cure the polymerand reduce its melt flow into the acceptable range of to 800. The virginpolymers are partially cured by heat treating in the absence of oxygenor with an oxidizing agent, either under vacuum or at atmospheric orsuperatmospheric pressure, to increase the molecular weight by either alengthening of a molecular chain or by crosslinking or by a combinationof both to improve such properties as tensile strength. Such treatmentcan be effected, for example, by heating the polymer preferably to anelevated temperature, either above or below the melting point of thepolymer, in some cases as high as 250C (482F) to 500C (932F). Such heat1 treatment can be carried out while contacting the polymer with air orunder vacuum or under an inert gas such as nitrogen. It has been foundadvantageous toeffect the curing of the polymer by contacting thepolymer with air at a temperature slightly below the melting point ofthe polymer.

The melting point of phenylene sulfide polymers can be readilydetermined by differential thermal analysis (DTA) by heating a 10 mgsample of the polymer at a rate of 10C per minute. The melting point ofthe polymer is taken from the DTA thermogram in a conventional manner.The temperature at which the polymer is cured will vary within the rangeof about to about 400C, depending upon the molecular weight and meltingpoint of the polymer. Generally, the curing temperature will be in therange of from about 25F (139C) to about F (685C), preferably from about50F (27.8C) to about 100F (55.5C) below the melting point of the polymerbeing treated. The time required for the curing treatment will besufficient to reduce the melt flow into the acceptable range and,depending on the melt flow of the virgin polymer, will range from a fewminutes to 15 hours or as long as several days. The curing time requiredis usually only a few hours. The preferred time for poly(phenylenesulfide), for example, is two to eight hours at a temperature rangingfrom about 50F (27.8C) to about 100F (55.5C) below the melting point ofthe polymer: the closer the treating temperature is to the melting pointof the polymer, the shorter the treating time required.

As indicated above, the curing or heating treatment is preferablycarried out in the presence of an oxygencontaining gaseous oxidizingatmosphere such as air. The oxidizing gas rate with respect tocontacting of the particulate polymer will vary appreciably, dependingupon the type of apparatus employed for carrying out the oxidativecuring. If desired, the air can be preheated prior to contacting withthe particulate polymer.

The curing or heating treatment can be carried out in conventionalequipment for the contacting of particulate solids with hot gases. Aconvenient method is to contact the particulate polymer with air in afluidizedsolids contactor using air as both the fluidization and curingmedium. The operation may be batch or continuous with batch preferred.Samples can be withdrawn periodically for measurement of melt flow todetermine when curing is complete.

As indicated previously, following the reduction in melt flow of thepolymer to the 75 to 800 range by heating, the polymer is then meltextruded using conventional polymer melt spinning equipment by passingTABLE I molten polymer through spinneret orifices of 5 to 40 HoursPolymer Sample Cured Melt m1ls dlameter. The melt spinning ls carriedouto at an el Nu at 500,]: Flow Fiber Properties evated temperature ofabout 25 to about 100 C above 5 the melting point of the polymer. Themelt spinning is l 0 0 tguda as ttl and u d not o o be rawn withoutbreaking. often carried out at about 600 F (316 C). The molten 2 l 390Somewhat bencrthan sample I but filaments are drawn from the splnneretorifices by could only be drawn to short lengths means of take-up rollsat a linear rate at least ten times 3 2 H4 g id I the linear extrusionrate: this reduces the diameter of 10 tii r gs ifi mii in stite i rigThis: in the filaments proportionally. The melt-drawn filaments 4 3 61 gg g: i gt are then cooled to approximately room temperature by 22 m mp uair contacting (commonly called an quenching) or by passage through awater bath. The now s0]id t te- Properties of the fibers obtained fromSample 3 in fil are h drawn again hi i i the li Table I were evaluatedat various temperatures as tabustate, at atmospheric or elevatedtemperature considerlated below In Table ably below the melting point,in order to orient the TABLE H polymer molecules and thus produce strongfibers. Draw ratios during the solid-state drawing step range Breakingal Initial from about 3 to about 8 times, Preferably from 3 to 6 jg g fi5'2; Tenacgym f l times, their original length. Th1s1s accomplished byopgr 8 gp tea 0 gp erating the take-up rolls at 3 to 6 times the speedof the 5 l8 193 -68 12 67 feed rolls. Between the two rolls thefilaments can be 22 3*? :3; 31%? 5 2 heated as by passage around aheated pin, over a 25 100 382 197 1.94 28 26 heated plate, by passagethrough a heated liquid, etc. 26 55 200 228 193 1.20 3l 6 EXAMPLE IPhenylene Sulfide polymer as produced by Example ""Tenacity obtained bydividing Breaking Strength by Denier. F m was used to fibers accord 30Referring to the above data, it is seen that breaking mg to ourinvention. The polymer initially had a melt Strength and tenacity remainhigh up to a temperature flow in excess of 2,000 grams per ten minutesas meaof about 150C and are still acceptable at sureod x M modlfied toOperate a 200C (392F). This is very good stability for fibers at 650 Fwith a p s ton load of 5 kilograms. Inherent VlS- Such i temperatures Thfib are l coslty of the initial polymer was 0.22 as measured in lburningwith an 0 (Limited Oxygen Index) f 35 Chloronaphthalene at 206C at a P yconcentra- (will not burn in an atmosphere containing less than 35 tionof 0.4 grams per 100 ml solution. volume percent oxygen).

The polymer was partially cured by heating with air EXAM L I at 500F(260C) with samples removed from the cur- P E I ing contactor after 1, 2and 3 hours in order to obtain Po1y(phenylene sulfide) with an inherentviscosity of samples with melt flows reduced to decreasing values. 0.24and cured to a melt flow of 32 could not be ex- The polymer samples weremelt spun into filam t truded smoothly into filaments and the extrudatecould using an lnstron Rheometer containing a single orifice not betaken p On a roll The melt flow of the P y with a diameter of 20 milsand a length of 176 mils. The was too low for extrudmg the P y Intofilaments.

O polymer was extruded at a temperature of 290 to EXAMPLE In 310C at arate of 1 ml per minute. The molten filaments were hand pulled from theorifice at a rate at Polywhenyleqe Sulfidg) havmgoan g' P Y least 10times the extrusion rate, passed through a of pamany at 288 C (550 F) fdlffer' water bath for quenching and then drawn in the solid ent perlodsof time to obtaln polymer samples with melt state at a draw ratio of 4by hand pulling over a hot flows vary mg from 154 to These samples wereplate melt spun lnto filaments by passage of the molten poly- A summaryof the results is presented below in Table mg through a cPnve.nnonalScrew pack and.s.pmneret I orifice of 20 m1ls drameter under theconditions and with results tabulated below.

TABLE III Melt Flow Melt Filament Solid-State Drawing Sample of CuredSpinning Takeup Temp., No. Polymer Temp., "C Speed, ft/min Ratio "C l77l 300 415 3 2 293 300 400 3 100" 3 279 300 3 15"" 3 100" 4 154 350Broke at Denier Initial Before Solid After Solid Tenacity, Elongation,Modulus State Draw State Draw gdenier gdenier l 93 29 L5 52 31 2 96 291.5 50 31 3 94 29 1.4 45 31 ""Would not run at 415 ft'min. "Could not bedrawn three times at l50C.

Properties of the fibers tabulated above are also very satisfactory forhigh-melting, non-burning polymers.

EXAMPLE IV Poly(phenylene sulfide) with an inherent viscosity of 0.18was partially cured to a melt flow of 390 and then melt spun at 310Cthrough a 6-orifice spinneret (orifice diameter of 9 mils) at 1 ml perminute. The filaments were drawn in the molten state at least 10 times,air quenched, and taken up on a roll at a rate of 75 feet per minute.The six filaments were drawn in the solid state by passage over a hotplate at 150C to four times their original length and then three-pliedto form a 356 denier, 18-filament yarn. Yarn tenacity was 1.12 grams perdenier; it had a 46% elongation at break and an initial modulus of 32grams per denier.

EXAMPLE V The yarn from Example IV was knitted on a Carolina ModelLabknit-l laboratory knitting machine, using a 3.5-inch-diametercylinder with 220 needles. The fabric thus knitted had 26 wales per inchand 35 courses per inch. The knitted fabric was flexible and had goodappearance and hand. It was chemically inert and nonburning (LOI of 35)suggesting suitability for filter cloths in high-temperature, corrosiveapplications, protective clothing, draperies, and upholstering in publicbuildings, etc.

We claim:

1. A process for the production of strong, highmodulus, high-melting,non-burning poly(phenylene sulfide) fibers having excellentcorrosion-resistant properties which comprises the steps of:

a. heating a phenylene sulfide polymer at an elevated temperature andfor a period of time sufficient to at least partially cure and lower themelt flow of the polymer to within the range of 75 to 800 grams per 10minutes as measured by ASTM method D-12- 38-70 modified to operate at650F with a piston load of kilograms.

b. melt spinning the partially cured polymer obtained in step (a) bypassing the polymer in the molten state through spinneret orifices at atemperature above the polymer melting point to produce filamentstherefrom, and c. drawing the molten filaments of step (b) by takingthem up on rolls at a linear velocity at least 5 times the linearvelocity of the polymer passing through the spinneret orifices to formsaid strong, high-modulus fibers.

2. A process according to claim 1 wherein the meltdrawn fibers of step(c) are again drawn in the solid state about three to about eight timesto produce poly(- phenylene sulfide) fibers with a high degree ofmolecular orientation that are strong and have excellent hightemperature properties.

3. A process according to claim 1 wherein the phenylene sulfide polymeris cured in step (a) by heating in the presence of an oxygen-containinggas.

4. A process according to claim 3 wherein the oxygencontaining gas isair and the temperature maintained during said oxidative heating iswithin the range 25-l25 F below the melting point of the phenylenesulfide polymer.

5. A process according to claim 3 wherein the phenylene sulfide polymeris precured to a melt flow in the range 100-500 by contacting with airand the inherent viscosity of the polymer prior to precuring is in therange 0.18 to 0.20, and the precured polymer is melt spun at atemperature of about 600 F, followed by melt drawing at least ten timesand then drawing in the solid state in the range of 4 to 8 times toproduce a strong, high-modulus poly(phenylene sulfide) fiber havingexcellent high temperature properties.

6. A process according to claim 1 wherein the phenylene sulfide polymeris cured in step (a) by heating in the presence of air at a temperaturewithin the range of 25-125 F below the melting point of the polymer, andsaid polymer melt is passed through spinneret orifices of 5 mils to 40mils diameter.

7. A process according to claim 1 wherein the phenylene sulfide polymerprior to heating has an inherent viscosity in the range of 0.15 to 0.25.

1. A PROCESS FOR THE PRODUCTION OF STRONG, HIGH-MODULUS, HIGH-MELTING,NON-BURNING POLY(PHENYLENE SULFIDE) FIBERS HAVING EXCELLENTCORROSION-RESISTANT PROPERTIES WHICH COMPRISES THE STEPS OF: A. HEATINGA PHENYLENE SULFIDE POLYMER AT AN ELEVATED TEMPERATURE AND FOR A PERIODOF TIME SUFFICIENT TO AT LEAST PARTIALLY CURE AND LOWER THE MELT FLOW OFTHE POLYMER TO WITHIN THE RANGE OF 75 TO 800 GRAMS PR 10 MINUTES ASMEASURED BY ASTM METHOD D-1238-70 MODIFIED TO OPERATE AT 650*F WITH APISTON LOAD OF 5 KILOGRAMS, B. MELT SPINNING THE PARTIALLY CURED POLYMEROBTAINED IN STEP (A) BY PASSING THE POLYMER IN THE MILTEN STATE THROUGHSPINNERET ORIFICES AT A TEMPERATURE ABBOVE THE POLYMER MELTING POINT TOPRODUCE FILAMENTS THEREFROM, AND C. DRAWING THE MOLTEN FILAMENTS OF TEP(B) BY TAKING THEM UP ON ROLLS AT A LINEAR VELOCITY AT LEAST 10 TIMESTHE LINEAR VELOCITY OF THE POLYMER PASSING THROUGH THE SPINNERETORIFICES TO FORM SAID STRONG, HIGH-MODULUS FIBERS.
 2. A processaccording to claim 1 wherein the melt-drawn fibers of step (c) are againdrawn in the solid state about three to about eight times to producepoly(phenylene sulfide) fibers with a high degree of molecularorientation that are strong and have excellent high temperatureproperties.
 3. A process according to claim 1 wherein the phenylenesulfide polymer is cured in step (a) by heating in the presence of anoxygen-containing gas.
 4. A process according to claim 3 wherein theoxygencontaining gas is air and the temperature maintained during saidoxidative heating is within the range 25*-125* F below the melting pointof the phenylene sulfide polymer.
 5. A process according to claim 3wherein the phenylene sulfide polymer is precured to a melt flow in therange 100-500 by contacting with air and the inherent viscosity of thepolymer prior to precuring is in the range 0.18 to 0.20, and theprecured polymer is melt spun at a temperature of about 600* F, followedby melt drawing at least ten times and then drawing in the solid statein the range of 4 to 8 times to produce a strong, high-moduluspoly(phenylene sulfide) fiber having excellent high temperatureproperties.
 6. A process according to claim 1 wherein the phenylenesulfide polymer is cured in step (a) by heating in the presence of airat a temperature within the range of 25-125* F below the melting pointof the polymer, and said polymer melt is passed through spinneretorifices of 5 mils to 40 mils diameter.
 7. A process according to claim1 wherein the phenylene sulfide polymer prior to heating has an inherentviscosity in the range of 0.15 to 0.25.